Secure communications between devices has always been a high priority in communication protocols. One present solution to implement secure communications is a Diffie-Hellman key exchange. Other security protocols also exist for key exchange, but Diffie-Hellman is one of the most well-known. The Diffie-Hellman key exchanges allows two communications devices to share a secret, such as a session key, that is used to establish a secure communications channel.
However, a problem with the Diffie-Hellman key exchange is the insecurity related to initially establishing and sharing the key between the two devices. A “man in the middle” can eavesdrop in this communication and compromise the secure communications channel. This is also called a “man in the middle” attack. Such attacks are a significant problem for wireless communications, such as Wi-Fi, because the access point is always in the middle.
A recent technological innovation in wireless communication is the tap transfer process. Tap transfer refers to the process of initiating a data transfer from one device to another by tapping them together to induce inductive coupling between the devices. Tap transfer presents a unique opportunity to securely establish a shared secret. First, to perform tap transfer, the two communications devices must be proximally located and, as such, become difficult to eavesdrop on. Second, tap transfer provides enough time (when up in very high radio frequencies) to transmit a couple of hundred bits worth of a secret.